石漠化治理下重庆酉阳典型岩溶槽谷区不同坡向地下水时空变化特征

Temporal and Spatial Variation Characteristics of Groundwater in Different Slopes under Rocky Desertification Treatments in the Typical Karst trough of Youyang,Chongqing

岩溶槽谷区独特的地质背景制约着地下水的空间分布和赋存规律,探究槽谷区地下水动态变化对石漠化治理具有重要意义。本文以重庆酉阳龙潭槽谷为例,在2017~2019年对槽谷地下水进行动态监测和采样分析,探究石漠化治理下典型岩溶槽谷不同坡向地下水时空变化规律。研究表明,槽谷区地下水对环境变化敏感,石漠化治理过程中不同程度农业活动直接影响着地下水水化学动态特征。强降雨期间,逆层坡坡面流全Fe、Al3+浓度峰值分别为1.3 mg/L、2.0 mg/L,是逆坡岩溶泉全Fe、Al3+浓度的13倍,表明轻度石漠化的逆层坡水土流失严重。逆层坡地表物质和土壤颗粒难以直接进入地下含水层,顺层坡雨水将地表或残留在裂隙、溶隙或管道等含水介质中的土壤颗粒或土壤营养元素迁移至水文系统中,土壤肥力下降。从空间上,顺逆坡石漠化裸岩出露差异所致的汇流机制、土层厚度和植被状况造成了顺逆层坡在"二水"转化上存在差异,对研究区地下水的时空变化有重要影响。

The unique geological background of karst trough valleys restricts the spatial distribution and occurrence of groundwater. It is important for the desertification governance to explore the dynamic changes and influencing factors of water resource in rocky desertification areas. This study selected the Longtan Trough Valley in Youyang,Chongqing,as an example,and dynamically monitored and sampled groundwater in the trough valley from 2017-2019 to explore its temporal and spatial variation in different slopes of a typical karst trough valley under the control of rocky desertification. Results showed that groundwater in the trough area was sensitive to environmental changes,and that agricultural activities of varied degrees in the process of rock desertification control directly affected the dynamic characteristics of groundwater hydrochemistry. During heavy rainfalls,the peak concentrations of total Fe and Al3+in the reverse layer slope flow were 1.3 mg/L and 2.0 mg/L,respectively,which were 13 times of those in the reverse slope karst spring,indicating the water and soil loss on the layer slope was serious. Rainwater on the slope carried soil particles and nutrients of the surface soil or other locations,such as fissures,crevices and pipes,into the groundwater system,and such rose the concentrations of K+,total Fe,and Al3+.Spatially,the confluence mechanism,soil layer thickness and vegetation conditions caused by different rocky desertification as well as the different " two-water" transformations on the reverse slope had significant effects on the spatial and temporal changes of groundwater in the study area.